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rdf:type |
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lifeskim:mentions |
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pubmed:dateCreated |
1993-2-2
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pubmed:abstractText |
1. Single atrial myocytes obtained by enzyme perfusion from hearts of adult guinea-pigs were investigated using whole-cell voltage clamp and Indo-1 micro-fluorometry. 2. In myocytes loaded with a solution containing citrate as a low-affinity, non-saturable Ca2+ chelator, two types of [Ca2+]i transients could be recorded during repetitive activation of L-type Ca2+ current. Both large and small [Ca2+]i transients occurred; large transients reached peak values of about 1 microM, and small transients were about 100 nM or less in amplitude. 3. In the case of the large transients, peak [Ca2+]i was usually reached with a variable delay after repolarization from a voltage step that activated calcium current (ICa). For the small transients the rise in [Ca2+]i paralleled ICa. Upon repolarization [Ca2+]i started to decay. 4. The small transients reflect entry of Ca2+ through Ca2+ channels (entry transients), whereas the large transients are due to entry and release from the sarcoplasmic reticulum (release transients). 5. The entry transients displayed a positive staircase pattern during trains of depolarizing voltage steps despite constant or even decreasing amplitude of ICa. The steepness of the staircase was increased by elevation of [Ca2+]o. Entry transients were always smallest immediately after a release transient. 6. After functional removal of the sarcoplasmic reticulum by caffeine (1-5 mM) the staircase pattern of the transients reflecting Ca2+ entry was abolished. 7. It is concluded that the staircase pattern is due to rapid uptake by the sarcoplasmic reticulum of Ca2+ entering the cell, resulting in an attenuation of the signal. The attenuation is strongest shortly after a release signal, when the rate of sequestration of Ca2+ by the SR should be highest. 8. Evidence is provided that a compartment of the SR is involved in attenuation of the entry transients. This compartment has been identified recently as a peripheral release compartment.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/1335504-14064358,
http://linkedlifedata.com/resource/pubmed/commentcorrection/1335504-1745604,
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http://linkedlifedata.com/resource/pubmed/commentcorrection/1335504-6641745
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
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pubmed:status |
MEDLINE
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pubmed:month |
Aug
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pubmed:issn |
0022-3751
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:volume |
454
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
321-38
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pubmed:dateRevised |
2010-9-7
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pubmed:meshHeading |
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pubmed:year |
1992
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pubmed:articleTitle |
Calcium transients caused by calcium entry are influenced by the sarcoplasmic reticulum in guinea-pig atrial myocytes.
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pubmed:affiliation |
Laboratory of Physiology, Catholic University Leuven, Belgium.
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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